Population dynamics of four species of Geocoris in the peanut agroecosystem

Abstract

The effect of temperature on development, survivorship, reproductivity, and longevity of Geocoris pallens Stal, Geocoris punctipes (Say), Geocoris uliginosus (Say), and Geocoris lividipennis Stal was studied at a series of constant temperatures ranging from 18.3(DEGREES)C to 43.3(DEGREES)C. Data from these investigations were used to calculate certain population statistics (i.e. T(,c), R(,o), r(,c), and R(,c)) for the various species. Temporal distribution of the four species of Geocoris was observed during three growing seasons (1977-1979) in peanut fields located in Comanche and Eastland counties, Texas. Life tables were constructed for both laboratory and field cohorts of Geocoris. Geocoris pallens completed development between 21.1(DEGREES)C-37.8(DEGREES)C; G. punctipes between 21.1(DEGREES)C-35.0(DEGREES)C; and G. uliginosus and G. lividipennis between 23.9(DEGREES)C-37.8(DEGREES)C. Developmental times for each life stage varied inversely with temperature, and developmental thresholds varied for each life stage. Survivorship of G. punctipes was more favorable below 32.2(DEGREES)C; whereas, survival of G. pallens and G. uliginosus was greater at temperatures above 32.2(DEGREES)C. Geocoris lividipennis appeared to be the least affected by changes in temperature but had the greatest mortality of the four species regardless of the temperature.